Symmetric LED array for pulse oximetry

• US 20080081972A1
• Filed: 09/29/2006
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Debreczeny, Martin P.
• Granted Patent: US 8,068,891 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

There is provided a sensor for pulse oximeter systems. The sensor comprises a first source of electromagnetic radiation configured to operate at a first wavelength, a second source of electromagnetic radiation configured to operate at a second wavelength, and a third source of electromagnetic radiation configured to operate at a third wavelength. The emission spectra of the first and third sources of electromagnetic radiation overlap at their half power level or greater and correspond to a center wavelength in the range of 650 to 670 nm.

Claims

1. A sensor for pulse oximeter systems comprising:

a first source of electromagnetic radiation configured to operate at a first wavelength;

a second source of electromagnetic radiation configured to operate at a second wavelength;

a third source of electromagnetic radiation configured to operate at a third wavelength, wherein the emission spectra of the first and third sources of electromagnetic radiation overlap at their half power level or greater and correspond to a center wavelength in the range of 650 to 670 nm; and

a photodetector configured to receive electromagnetic radiation from blood-perfused tissue irradiated by the first, second and third sources of electromagnetic radiation.

2. The sensor of claim 1, wherein the first and third sources of electromagnetic radiation emit in the red region of the electromagnetic spectrum.

3. The sensor of claim 1, wherein the first source of electromagnetic radiation has an emission maximum at less than 670 nm and the third source has an emission maximum in greater than 650 nm, the emission maximum of the third source occurring at a wavelength greater than the emission maximum of the first source and wherein the first and third sources of electromagnetic radiation are spectrally equidistant from the center wavelength.

4. The sensor of claim 1, wherein the first and third sources of electromagnetic radiation are spatially oriented symmetrically about an axis wherein the axis bisects the second source of electromagnetic radiation.

5. The sensor of claim 1, wherein the second source of electromagnetic radiation is configured to emit in the near-infrared region of the electromagnetic spectrum.

6. The sensor of claim 1, wherein the second source of electromagnetic radiation is configured to emit in the infrared region of the electromagnetic spectrum.

7. The sensor of claim 1, wherein the photodetector is coated with a material that limits the spectral bandwidth of detected light.

8. The sensor of claim 7, wherein the material comprises a multilayer dielectric film.

9. The sensor of claim 7, wherein the material comprises a light-absorbing dye.

10. The sensor of claim 1, wherein at least one of the sources is coated with a material that limits the spectral bandwidth emitted light.

11. The sensor of claim 10, wherein the material comprises a multilayer dielectric film.

12. The sensor of claim 10, wherein the material comprises a light-absorbing dye.

13. A system for determining physiological parameters comprising:

a sensor comprising;

a first light emitting diode (LED) configured to emit radiation in the red region of the electromagnetic spectrum, the first LED having a maximum wavelength less than 670 nm;

a second LED configured to operate in the near-infrared region of the electromagnetic spectrum;

a third LED configured to operate in the red region of the electromagnetic spectrum, the third LED having a maximum wavelength greater than 650 nm, the third LED having a maximum wavelength greater than the first LED, wherein the first LED and third LED are spectrally symmetrical with respect to a center wavelength in the range 650 to 670 nm; and

a photodetector configured to generate a signal corresponding to received electromagnetic radiation from blood-perfused tissue irradiated by the first, second and third sources of electromagnetic radiation; and

a pulse oximeter configured to compute physiological parameters based on the signals generated by the photodetector.

14. The system of claim 13, wherein the first LED and third LED are spatially oriented symmetrically about an axis relative to the second LED.

15. The system of claim 14, wherein the sensor comprises a curved surface configured to allow optical coupling of a patient'"'"'s finger with the first, second and third LEDs, and the photodetector.

16. The system of claim 15, wherein the curved surface inhibits axial movement of the patient'"'"'s finger.

17. A method for determining physiological parameters using a pulse oximeter comprising:

transmitting electromagnetic radiation from a first light emitting diode (LED), a second LED and a third LED, wherein the first and third LEDs operate concurrently and have emission spectra in the red region of the electromagnetic spectrum, the emission spectra overlapping at greater than or equal to a half power level of the respective emission spectra causing a peak corresponding to a center wavelength;

generating a photoelectrical current corresponding to the electromagnetic radiation from the first, second and third LEDs; and

computing physiological parameters based on the photoelectrical current.